Mirai Ninja: Keigumo Kinin Gaiden (Future Ninja: Stealth Joy Cloud Device Side Story), known as Cyber Ninja in the United States, Warlord in Canada and Robo Ninja in the UK, is a 1988 Japanese science fiction action film directed by Keita Amemiya, which was co-produced and released by Namco that premiered on October of 1988 at the Tokyo International Fantastic Film Festival.

In a future time a war is being waged between humans and cyborgs. One of the elite cyberninja of the enemy goes rogue and sets out to assist the royal family after their headstrong princess is captured and destined to become the final sacrifice needed to summon the cyborg legions digital overlord from another dimension. The resistance army sends a small band of soldiers in, among whom is a determined young man out to avenge the death of his brother at the hands of the robots. After suffering many losses and battling towards the enemy castle it is revealed that the cyberninja Shiranui is in fact the lost brother, transformed into the robot and now determined to regain his human body. The survivors must storm the technological castle and rescue the princess before the resistance army fires a super cannon to prevent the summoning of the electronic evil.